1. Field of the invention
The present invention relates to devices for applying an adhesive-backed cover seal to a microplate and, more particularly, to an improved microplate cover seal applicator having easily manipulatable pressure application means which may be brought into and out of contact with the microplate without significant effort by the user, and an operating mechanism that allows long-term, continuous use of the apparatus without risking injury to the user.
2. Description of the Background
In the chemical processing and testing of liquid samples, disposable plastic trays are often utilized having a plurality of open top wells, the plurality of wells allowing a single test tray to hold a multitude of specimens. Such test trays (or xe2x80x9cmicroplatesxe2x80x9d) ordinarily comprise a lightweight, integral molded plastic disposable unit having a large number of open wells, each of which are configured to receive a minute sample of the analytes to be tested and analyzed.
For several reasons, it has been found preferable to provide the open top face of such microplates with a covering. One key reason for doing so is the necessity of preventing the evaporation of the fluids contained in the wells to ensure the integrity of each test sample. Such covers also serve to prevent the inadvertent spillage of each well""s contents during transport from one location to another, prevent cross contamination between individual wells, and provide a generally sterile and controlled environment under which the testing and analysis of the fluids contained in the wells may be carried out.
The covers which are normally applied to such microplates generally comprise a thin, flaccid, pressure sensitive adhesive film configured to be applied to the top face of the microplate. In use, the film is applied to the top, open face of the microplate with its adhesive backing facing the top face of the microplate, such that the film is positioned over each of the individual open top wells. A roll braver is then run back and forth across the top face of the plate several times in all directions in an attempt to ensure uniform adhesion to the plate. Unfortunately, laboratory technicians are often required to seal microplates hundreds of times in a single day, and the long term gripping of a traditional brayer to roll the brayer in all directions over the top surface of the microplate quickly causes hand fatigue and can ultimately lead to such serious conditions as Carpal Tunnel Syndrome.
Attempts have been made in the past to provide an alternate method of applying a cover seal to the open top face of a microplate. For example, U.S. Pat. No. 4,002,009 to Tolosa et al. discloses a tape dispenser and tray sealer device having a rectangular base and upstanding parallel plates which hold a tape roll and a press roll. An oversize, hand-manipulable knob is provided for manual rotation of the press roll. The base is provided with guide rails for a microplate, and a cutter assembly sits beneath the press roller to cut the continuous sheet of tape after it is applied to the plate. In use, an operator places a filled tray on the guide rails and slides the tray towards the press roller. Once the tray comes in sufficient contact with the press roller to allow the press roller to grip the tray, the operator changes his or her grip from the tray to the knob, and rotates the knob to both drive the tray along the base and to apply the cover tape to the top face of the tray as it travels beneath the roller. Such method of applying a sealing tape to a microplate is time consuming and is prone to causing fatigue or even injury in the operator who is required to seal hundreds of plates in a single work shift.
Still other mechanisms have been provided for aiding in the application of a film to a blister type package for holding and dispensing pills. For instance, U.S. Pat. No. 5,622,028 discloses a pharmaceutical unit tray sealing apparatus having a base with a top horizontal surface formed from FORMICA, guides running parallel across the horizontal top face to guide the tray during the sealing operation, and a downwardly spring biased roller which is made operable by an electric motor. In use, an adhesive backed sheet is placed over the tray, and the tray is manually pushed towards the roller until drawn under the roller by its rotation. The roller is mounted in pillow blocks which are moved upward from their at rest position on the base when engaged by a microplate of suitable height. However, no provision is made for allowing a uniform compressive roller force to be applied to a tray regardless of its height.
Likewise, U.S. Pat. No. 4,835,945 to Perloff discloses a press for closing a redi-pak medication card comprising a bed having openings to accommodate a tray. A cavity card having one surface coated in selected areas with a pressure sensitive adhesive is placed on the tray, and then a pivoted cover is brought down and a pressure bar swivelled in place to exert pressure on the cover to seal the card and plastic sheet together. Once again, such a process is quite time consuming for the user who is attempting to seal several hundred cards in a single work shift.
Finally, U.S. Pat. No. 4,612,755 to Cavanaugh discloses a press for laminating a barrier film to a blister pack comprising a two-cycle reciprocatory carriage assembly including a tray for holding a blister pack and reciprocating the blister pack into and out of a housing. During a first cycle, a barrier film is prevented from contacting the blister pack by means of a pair of rollers which back the film away from the blister pack a predetermined distance. During the second cycle, the rollers advance the barrier film toward and in contact with the blister pack to apply the film. Such a device is highly complex and time consuming, making it impractical for use in an environment requiring the constant, repetitive sealing of up to hundreds of units in a single work shift.
Moreover, each of the above-cited references which use a press roller to seal an adhesive sheet to either a blister pack or microplate do not allow multiple bidirectional passes of the microplate beneath the press roller. It has been found that due to imperfections in the top surface area of standard microplate, more than a single two-cycle (i.e., forward and rearward) pass of the microplate and adhesive sheet is often necessary in order to provide a fully secure bond between the adhesive sheet and the top face of the microplate, even when using a resilient roller which might adapt its surface to such varying contours. Where a motor drive is utilized (as in Harp ""028), the microplate must be passed under the roller in only one direction, removed from the exit side of the apparatus, placed back on the entry side of the apparatus, passed under the roller. etc., until sufficient passes have been accomplished to provide a sufficient seal. Such process is highly time consuming and inefficient for typical laboratory scenarios in which hundreds of microplates must be sealed and processed each day. Likewise, where a spool of adhesive tape is to be sequentially applied to a microplate (as in Tolosa et al.), reversal of the microplate under the press roller will either remove the cover tape that had just been applied, or result in an additional layer of the adhesive film being applied to the surface of the microplate with the adhesive portion pointing upwards from the top face of the microplate, both of which are undesirable results. Similarly, attempting to pass the microplate below the press roller through more than one bi-directional cycle in which a tape layer is applied in a single bi-directional cycle (as in Cavanagh ""755) will likewise result in the unwanted application of multiple layers of adhesive film on the top face of the microplate.
It would therefore be advantageous to provide a microplate cover seal applicator which eases fatigue on the user who is required to apply hundreds of covers in a work shift, while ensuring an assembly which is easy to use, may be manufactured at low cost, and allows the seal to be applied very rapidly.
Further, as microplates are provided in a variety of heights, it would be highly advantageous to provide a press roller which could uniformly apply sealing pressure across the entire width of the top face of a microplate irrespective of the height of the microplate. Such a device should be adaptable so as to enable the press roller mount to be selectively positioned and locked at any desired height which corresponds to the height of the microplate to be sealed, while still enabling the press roller to be vertically displaced with respect to this raised mount position when it comes into contact with the microplate""s top face. This would ensure application of a sufficient amount of uniform pressure across the face of a microplate of any height.
Finally, to best ensure uniform application of a sealing force applied from a press roller, it would be advantageous to provide a rigid support for the entire surface area of the bottom of the microplate, as the failure to do so may result in a standard plastic microplate flexing into openings in a support on which it is placed, making it even more difficult to apply a uniform sealing force to the top face of the microplate.
It is, therefore, an object of the present invention to provide a microplate cover seal applicator which avoids the disadvantages of the prior art.
It is another object of the present invention to provide a microplate cover seal applicator which reduces fatigue on the user.
It is still another object of the present invention to provide a microplate cover seal applicator which is readily adaptable to receive microplates of any height while ensuring uniform force distribution across the width of the top face of the microplate irrespective of its height.
It is yet another object of the present invention to provide a microplate cover seal applicator in which movement of the microplate beneath a force application means is carried out through a moveable carriage supporting the entire bottom surface of the microplate.
It is still yet another object of the present invention to provide a microplate cover seal applicator having means to easily adjust the vertical position of a force-applying means in order to provide a desired sealing force to a microplate of any height, and means to easily lock and release the force-applying means from such position.
It is even yet another object of the present invention to provide a microplate cover seal applicator which is compact and easily transportable from table-top site to table-top site.
It is still even yet another object of the present invention to provide a microplate cover seal applicator which enables multiple, repetitive, bi-directional movement of the microplate under the sealing means.
According to the present invention, the above-described and other objects are accomplished by providing a microplate cover seal applicator comprising a rigid base comprising generally parallel side panels, a microplate support tray slidably mounted between the base side panels, a roller mount pivotally attached to each of the side panels, and a roller freely rotatably mounted within the roller mount. Each of the side panels are attached to two horizontal support bars, each of which in turn are supported above two suction cups enabling the removable but rigid positioning of the device on any flat surface. The microplate support tray is mounted for reciprocating horizontal movement between the side panels of the base, and is operatively connected to a manually operable handle which may be rotated both clockwise and counterclockwise any number of times to repetitively traverse the support tray forwards and rearwards between the side panels and below the roller. The support tray is provided with a shallow well dimensioned to receive a standard multi-well microplate. The roller mount positions the press roller overtop the support tray, and is configured such that the entire roller mount assembly may be pivoted about a pivot point located adjacent the back end of the device to raise the press roller away from the support tray and any microplates mounted thereon. The vertical position of the roller mount, and thus of the roller itself, may be locked in place with respect to the vertical support tray via a locking arm or knob on each side of the roller mount, thus enabling the roller to be used to apply a sealing force to microplates of varying heights. The roller is mounted within the roller mount via sliding blocks which rotatably hold the axle of the roller, which blocks are downwardly biased by resilient means to apply compressive force to the top face of a microplate positioned on the tray. The force applied by the roller may be adjusted through both modifying the height of the roller (through pivoting the roller mount assembly), or through adjusting the compression exerted by the resilient means on each sliding block.